1. Field of the Invention
The present invention relates to a method of forming a tungsten-coated W—Cu composite powder using a tungsten oxide (WO3 and WO2.9) powder and a copper oxide (CuO and Cu2O) powder and a use of the same, and more particularly, to a method of forming a W—Cu composite powder, which has a structure that tungsten grains surround a copper particle, by mixing and pulverizing tungsten oxide powder and copper oxide powder using turbular mixing or ball milling, reducing the Cu particle firstly at 200˜400° C. under a hydrogen atmosphere or a reducing gas environment including hydrogen, generating W nuclei on the reduced Cu powder at 500˜700° C., and growing the generated W nuclei at 750˜1080° C. as well as a use of the same for the use of powder injection molding.
2. Background of the Related Art
A method of forming a tungsten-coated W—Cu composite powder according to the related art includes the steps of reacting APT (ammonium paratungstate) or AMT (ammonium metatungstate) with CuO or CuOH just to form an intermediate product having a composition of CuWO4, mixing the CuWO4 with a tungsten oxide (WO3) powder with a proper ratio, and carrying out reduction thereon under a hydrogen atmosphere (U.S. Pat. No. 5,956,560). Yet, such a method essentially needs the step of forming the intermediate product of CuWO4.
And, Korean Patent No. 10-115587 discloses the steps of pulverizing and mixing tungsten oxide (WO3 or WO2.9) with copper oxide (CuO) uniformly by high energy ball milling and carrying out 2-step reduction thereon under a hydrogen atmosphere just to form a ultra-fine W—Cu composite powder. In the W—Cu composite powder formed by such a method, Cu and W are mixed independently with each other so as to be unsuitable for compacting as well as used as a powder for powder injection molding.
Many efforts have been made to overcome the problems of the related art, whereby a 3-step thermal reduction treatment is introduced just to develop a method of directly forming a tungsten-coated copper powder, i.e. a W—Cu composite powder, which has a structure that tungsten grains surround a copper particle, from a tungsten oxide powder and a copper oxide powder. A W—Cu composite powder where a Cu particle is surrounded by tungsten grains according to the present invention has a proper size as well as a round shape, thereby having a powder-feeding characteristic better than that of the related art. Therefore, compared to the method of the related art, the method according to the present invention provides excellent characteristics of compacting and powder injection molding.